(Or why Inherent Vice will never be recognized as Thomas Pynchon's best novel.)
I'm not saying that it is his best novel. I'm not ready to make that kind of assessment yet, and my choice would probably still be Mason & Dixon. However, the reasons why IV will never be recognized that way have nothing to do with its quality.
1) People are impressed by big books. There is a general idea, held by people who have never written either a novel or a short story, that writing novels is more difficult than writing short stories, and writing very big books is more difficult than writing shorter ones. As if albums with twenty songs are automatically better than ones with ten songs. As if "more difficult" = "better art." I was reading Mason & Dixon on the subway once, and the guy sitting next to me said, "I didn't think anybody ever finished his books." I had already read the book at least once, but I didn't mention that.
My experience, however, is that, in writing, shorter is the most difficult thing to do well. Ulysses is an amazing achievement, but "The Dead" is a better work of art.
And difficulty doesn't equate to quality. From what I've read, Rex Stout, probably my favorite mystery writer, wrote each of his Nero Wolfe novels in a few weeks, from the beginning straight through to the end, no rewrites, and then took the rest of the year off.
2) People think serious novels are more significant than funny ones, and IV is Pynchon's funniest novel yet. That's one assessment I am ready to make, though nothing in it is quite as hilarious as the disgusting English candy drill in Gravity's Rainbow, or the shenanigans at the Vrooms' house in Mason & Dixon.
Okay, maybe it isn't the funniest, but it is the goofiest. And it has the most sex, the most drugs, and the most rock and roll. And it probably involved less research than some of the others. So, it's definitely less impressive to the people who get impressed by the sorts of things that impress Academy Awards voters (who usually like movies which are long, historical, serious, and involve lots of suffering). However, as in I Heart Huckabees, the funniest stories are sometimes the most profound, though they are often not recognized as such because of people's prejudices on this subject.
Which may relate to the schism between people who think Shakespeare's greatest achievements are the big tragedies (Hamlet, Macbeth, etc.), and people like Orson Welles and Harold Bloom who think his greatest achievement was creating Falstaff.
3) Plus, of course, IV is a genre story (a mystery) and people have their prejudices about that, too.